Numbers on Ford flatheads is a very inexact science. Most numbers you'll find are only local foundry casting numbers, and so far no one has catalogged them.
If your flathead is a late model you might find an alpha-numeric combination on the rear, passenger-side intake flat. See the accompanying link.
Otherwise, you'll only be able to pin it down to a specific range of years. Collect numbers off the heads, watching for things such as a string that contains the numbers 6049/50 (Ford's right/left head pn) with a prefix like 18, 48, 99T 59, 8BA, EAB, etc.
Also, general things: How many fasteners (studs/bolts) on each head? 17, 21 or 24?
Where are the waterpumps? On the front of the block or on the heads?
When you get this info gathered, let me know and I'll go into more specific details.
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